There are over 20 major cable-stayed bridges in the U.S. and about 600 worldwide. Under certain combinations of light rain and moderate wind speeds (10 to 15 m/s), incidences of large-amplitude vibrations (on the order of 1 to 2m) of stay cables have been reported worldwide. It has been found that the rain-wind cable vibrations are often related to higher mode vibrations instead of the fundamental mode, implying that the tuned mass damper (TMD) designed for the first mode vibration is most likely not effective for higher mode vibrations. Traditional mechanical dampers are usually installed at the cable ends, which is not optimal for damping efficiency. The objective of this study is to develop a TMD that will adapt itself to deal with different cable vibrations, whether first mode or higher (Fig. 1). The adaptive TMD will be designed by using controllable magnetorheological (MR) fluids that are the magnetic analogs of electrorheological (ER) fluids. The study is divided into three phases.
